This passed me by completely, but new small engine emission legislation came into force on January 1st 2019.
This Stage V legislation covers diesel engines used in non-road mobile machinery, such as wood chippers, stump grinders, mowers and skid steer machinery.
It seeks to limit emissions ( much like the Euro 5, 6 diesel legislation ) currently being implemented by car & van makes and seen in practical effect with low emission zone charges in major cities.
Luckily (?) for us it is not retrospective, nor prohibits or end-of-life’s our ability to use, sell or buy 2nd hand machines BUT new machinery will need to adhere to this standard once stocks of pre Stage V engines have run out ( these stopped being made on 31st Dec 2018).
Apparently it could mean a move away from diesels back to petrol engines for new machinery in our industry in coming years, however I’m sure with matching increased purchase / running costs.